‘12 ALTERNATING GENERATORS AND SYNCHRONOUS MOTORS. 
Curve No. 1, represents the friction and ventilation losses in 
terms of the input expressed in K.W.; curve No. 2, is that of 
the iron losses; curve No 3, gives the field copper losses; 
curve No. 4, gives the armature copper losses; and curve 
No. 5, indicates the efficiency of the machine at different 
values of input, when the phase displacement is assumed 
equal to cos gp = 1. : 
It should be noted that the efficiency curve starts at an 
abscissa of 17.5 K.W. which represents the no-load losses, 
composed of the friction, iron and the minimum excitation 
losses. The energy consumption in the armature copper 
at no-load is insignificant and negligible. 
449, Efficiency.—The efficiency is the ratio between the useful 
output and the useful output plus all the losses expressed 
b 
z = H.P. x 746 
FP. X 746+ WLW Want We 
and in the present case the full load efficiency is equal to 
450 x 746 —94% 
1450 x 746-+3,900+-9,400+42,700--6,500- “° 
with a power factor cos p=l. 
...(43,) 
DESIGN OF A REVOLVING FIELD TYPE THREE 
7 | PHASE SYNCHRONOUS MOTOR. 
450. General Specification.—A three phase synchronous — 
motor of the revolving field type is to be designed with a 
star connected armature for a terminal pressure of 3,460 
volts and a speed of 375 revs. per minute, when supplied 
with a current at 50 cycles. 
The normal mechanical capacity of the motor is 550 H.P., but 
the machine should be capable of carrying a wattless lead- 
ing current, so that a power factor of cos p = 0.9 is ob- 
tained. al 8d ? 
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